This invention has to do with a method and apparatus for tensioning coiled springs that are usually mounted upon a central shaft and is specifically directed to a coiled spring that is mounted on a fixed shaft and used in providing the proper counterbalancing tension for use with overhead garage door openers.
The installation of overhead garage doors usually involves installing railings that support each side of the door and upon which the sides of the door are freely slideable. The railings usually have three sections which comprise an upper section in an horizontal position for storing the door in an open position, a vertical section for holding the door in a closed position, and a curved section for transition of the sides of the door from the horizontal rails to the vertical rails. As most garage doors are too heavy for a normal person to lift some sort of counterbalancing mechanism is usually provided so that the full weight of the door is not encountered when the door is transferred to the vertical sections of the railings when one closes the garage door. Even with power operated door opener devices a counter balance mechanism is provided so as to be able to reduce the horsepower requirements of the drive motor. For safety reasons the counter balancing mechanisms are also necessary in the event of failure of the garage door openers.
A prevailing type of counterbalancing mechanism in wide use with such overhead garage door openers, especially ones that have power operated motors to assist the opening and closing of the doors, is a coiled spring mounted upon a rotatable shaft. The shaft is usually located above the opening that is to be covered by the door and is transversely located across the path of the door. Upon this shaft is mounted a coiled spring in a somewhat concentric manner such that the longitudinal centerline of the spring approximately locates upon the longitudinal centerline of the shaft. One end of the spring is fixedly attached to a structure upon which the shaft is rotatably mounted and the other end of the spring is held releasably attached to the rotatable shaft. A cable arrangement is usually attached to the rotatable shaft in such a manner that it may be wound and unwound from the shaft. The other end of the cable is usually attached to the lowermost end of the door. Raising the door is supposed to cause the cable to wind around the shaft and lowering the door is supposed to cause the cable to unwind from the shaft.
The tensioning for the garage door takes the form of adjusting the tension exerted by the coiled spring upon the rotatable shaft that also holds the wound cable. When properly adjusted the tension exerted by the spring is supposed to just about counterbalance the weight of the door that is being transferred from the vertical section to the horizontal section of the railings. This is accomplished because, as the door travels downward the cable turns the rotatable shaft and in doing so winds the coiled spring mounted upon the shaft into a tighter configuration thereby producing an even greater upward counterbalancing effect on the weight of the door.
In original installation of the doors, when replacing broken springs, and even during periodic maintaince, it is necessary to adjust the tension of the coil springs to the desired degree so that the door can close and counterbalance almost the entire weight of the door during the raising and lowering of the door. To adjust the tension of the coiled spring it is necessary for one to loosen the releasably fixed end of the coil spring that is attached to the rotatable shaft and rotate the end of the spring relative to the shaft, either in a manner to lessen the tension or to tighten the tension. The coiled springs used in such installations are not insubstantial in the force and/or torque that they exert to accomplish their task and it is therefore considered by those skilled in the art a potentially dangerous operation. When the one end of the spring attached to the rotatable shaft is loosened it must be securely held so as not to freely uncoil back to a tension free state. Such an uncoiling while a workman or other person is in the area has produced some very severe injuries.
Recognition of the problem and attempts at solving the problem are illustrated by the U.S. Pat. No. 4,253,350 granted to De Tarr.
It is an object of the present invention to provide a safe and efficient method for the tensioning of coiled springs used in overhead garage door installations.
It is an object of the present invention to provide an improved tool for use in properly tensioning coiled springs used in overhead garage door installations.
It is an object of the present invention to provide a new attachment for coil springs that will ease the operation of adjusting the tension of coiled springs in overhead garage door installations.
It is an object of the present invention to provide a set of tools for use in adjusting the tension in overhead garage door supports.
According to the present invention there is disclosed an overhead garage door support arrangement which comprises a fixed support structure usually in the form of structural trusses placed on the walls or suspended from a ceiling of a garage. The support structure has thereon the railings and other mechanisms necessary for the operation of a garage door and specifically supports an elongate rotatable shaft usually mounted transverse to the travel of the door. An elongate coil spring having opposing ends and coils surrounds the shaft, with one of the opposing ends of the coil spring non-rotatably attached to the support structure, usually one of the side walls of the garage.
The present invention has to do with a collar rotatably mounted upon the shaft, the collar having a first means thereon for non-rotatable attachment to the opposite end of the coil spring attached to the wall. The collar is also provided with a second means for releasably holding the collar non-rotatable with the shaft. Extending from the collar or integrally on the collar is a boss means having longitudinally extending and outwardly projecting abutment surfaces formed thereon, with said projecting abutment surfaces having a greater longitudinal dimension than outward extending dimension. Preferably the boss will comprise a cylindrical, externally splined, rod section.
Preferably the first means on the collar comprises a frustro conical section with its base joining the collar and an abutment surface formed at such junction. Grooves are provided circumferential in a threadlike manner on the external part of the conical section to threadedly engage the radially inner surfaces of the coils and hold the end of the spring non-rotatably (in one direction) against the abutment surface. The grooves, abutment surface, and coils then comprise co-operating elements of threaded abutment means between the collar and the coils on one end of the spring. The collar is also provided with the ability (second means) to be releasably held non-rotatable with the shaft. The second means on the collar comprises threaded perforations extending from the outer diameter of the collar to the internal diameter that engages the shaft, and set-screws rotatably mounted in the perforations that may be advanced against the shaft to firmly hold the collar and shaft non-rotatable with one another. Preferably the collar is formed so that the first means and the boss means are separated by an intermediate section, with the intermediate section having a larger diameter than either of the first means and the boss means, and the intermediate section having the threaded perforations formed therein.
In addition to the other features formed on the collar of the present invention blind holes are also formed radially inwardly on the intermediate section of the collar.
The present invention further contemplates a collar and boss attachment mechanism for over head garage door support arrangements which comprises a collar rotatably mounted upon a cylindrical shaft, with a first means on the collar for fixed attachment to one end of the coiled spring mounted on the shaft and a second releasable means for holding the collar non-rotatable with respect to the shaft. Extending from or mounted integrally on the collar is a boss having longitudinally extending grooves formed on the outer periphery of the boss, with the grooves having a greater longitudinal extending dimension than the corresponding radially inward extending dimensions. The boss preferably takes the form of a cylindrical, externally splined, rod section.
Preferably the collar and boss attachment mechanism according to the present invention will have a first means comprising co-operating elements of threaded abutment connection between the collar and the coils on one end of the spring. Preferably the co-operating elements of threaded abutment means between the collar and the coils on one end of the spring comprise a circumferential threaded frustro-conical portion for engagement internally of the coils of the spring, and a longitudinally facing abutment surface at the base of the frustro-conical section engaging the end of the spring.
Preferably the collar and boss attachment mechanism according to the present invention will have a second means comprising radially extending threaded perforations, and set screws mounted in said perforations and operable to clamp said collar non-rotatably with said shaft. Preferably the first means and the boss are separated by an intermediate section, with the intermediate section having a larger diameter than either of the first means and the boss, and the intermediate section having the second means formed therein. And further the collar and boss attachment mechanism according to the present invention will comprises blind holes formed radially inwardly on the intermediate section. Such blind holes will have both circular and hexagonal configurations when viewed from above.
The present invention also contemplates an adapter and boss attachment mechanism for tensioning coiled spring assemblies already in place. Such attachments comprises an adapter for rotatable mounting upon a cylindrical shaft, with a first means on the adapter for releasable attachment to a collar attached to one end of a coiled spring mounted on the shaft, and a boss on the collar with the boss having longitudinally extending grooves formed on the outer periphery of the boss with the grooves having a greater longitudinal extending dimension than the corresponding radially inward extending dimensions. Preferably the boss will comprise two symmetrized sections with a hinge means joining said sections along their symmetrical centerline, so that the boss has a closed position in which it is rotatably mounted upon the shaft and an open position in which it may be removed from or positioned around the shaft. And even more preferably either one or both the adapter and boss of the adapter and boss attachment mechanism will comprise two symmetrized sections with a hinge joining the sections along their symmetrical centerline so that the adapter and boss have a closed position in which the adapter engages the collar and the boss means engages the shaft, and an open position in which the adapter may be removed from or positioned on the collar and the boss may be removed from or positioned on the collar, and means for holding the sections in a closed relationship.
The present invention further contemplates a wrench assembly which comprises an elongate handle and an open ended jaw formation, located on one end of the handle, for closely surrounding and engaging a majority of the perimeter of a cylindrical shaft. Located in the handle is a spring loaded latch mechanism moveable latch that, in a first position, protrudes into the jaw engagement area and, in a second position is retracted from the jaw engagement area. Provided on the wrench is a means for moving the latch from either one of the first position or second positions to the other of the positions. The means for moving the latch can take the form of a lever pivotally mounted on the handle but most preferably the means for moving the latch will take the form of co-operating elements of a rod and cam assembly, where the rod extends through the interior of the handle and engages a cam mechanism, so that rotation of the cam mechanism operates the latch from one of its first or second positions to the other position.
The present invention also contemplates a method of winding a coil spring which is mounted upon a rotatable shaft. This method comprises the steps of rotatably mounting upon the shaft a body having an internal hollow cylindrical configuration and providing external splines on the body. Next the body is attached non-rotatably to the end of the spring that is releasably attached to the shaft, and two wrenches according to the present invention are engaged over the splines. One of the wrenches is then activated to engage the splines so as to hold the body against movement. The end of the spring is then released from attachment with the shaft. The engaged wrench is then moved so as to rotate the body and the end of the spring in the direction desired. The engaged wrench is then again held against movement while the other wrench is positioned to provide further rotation to said body and spring and then activated to engage the splines on the body. While holding the engaged wrench against movement the first wrench is dis-engaged from the spline and the engaged wrench is then moved so as to rotate the body and the end of the spring in the direction desired. This procedure is repeated until the desired tension has been achieved in the coil spring. The end of the coil spring is then re-attached and the wrenches are removed from the spline area.
Preferably the material for the boss means and the collar is comprised of a stainless steel material and most preferably a iron-chromium corrosion resistantant stainless specified as type CA-15 by the Steel Founders Society of America and by the Alloy Casting Institute. The material is appropriately heat treated after machining to obtain the maximum hardness.